{"gene":"METTL17","run_date":"2026-04-28T18:30:28","timeline":{"discoveries":[{"year":2019,"finding":"METTL17 localizes to mitochondria via an N-terminal targeting sequence, directly binds 12S mitochondrial ribosomal RNA (mt-rRNA) and small subunit proteins (MSSUs), and functions as an SAM-binding protein. Loss of METTL17 reduces m4C840 (~70%) and m5C842 (~50%) modifications on 12S mt-rRNA, destabilizes 12S mt-rRNA and MSSU proteins, and impairs translation of mitochondrial protein-coding genes, disrupting OXPHOS and cellular metabolome in mouse ESCs.","method":"CRISPR knockout screen, subcellular fractionation/localization, Co-IP with mt-rRNA and ribosomal proteins, SAM-binding assay, mass spectrometry for rRNA modification quantification, mitochondrial translation assay","journal":"FASEB journal","confidence":"High","confidence_rationale":"Tier 1–2 — multiple orthogonal methods (localization, RNA binding, SAM-binding biochemistry, modification quantification, translation assay) in a single study with rigorous controls","pmids":["31487196"],"is_preprint":false},{"year":2024,"finding":"METTL17 harbors a previously unrecognized [Fe4S4]2+ cluster required for its stability and binds to the mitoribosomal small subunit during late assembly. It acts as an Fe-S cluster checkpoint, promoting mitochondrial translation of Fe-S cluster-rich OXPHOS proteins only when Fe-S cofactors are replete. METTL17 overexpression rescues mitochondrial translation and bioenergetic defects in frataxin (FXN)-depleted cells.","method":"Comparative sequence analysis, site-directed mutagenesis, biochemistry (Fe-S cluster characterization), cryo-electron microscopy, quantitative proteomics in FXN-deficient cells, overexpression rescue experiments","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 — cryo-EM structure, mutagenesis, in vitro biochemistry, and functional rescue, replicated across multiple methods in one rigorous study","pmids":["38199006"],"is_preprint":false},{"year":2024,"finding":"METTL17 depletion in colorectal cancer cells reduces mitochondrial RNA methylation (m4C, m5C, m3C, m7G, m6A), impairs translation of mitochondrial protein-coding genes, disrupts mitochondrial function and energy metabolism, and enhances lipid peroxidation and ROS, sensitizing cells to ferroptosis. METTL17-interacting proteins involved in mitochondrial gene expression are also required for ferroptosis resistance.","method":"siRNA/shRNA knockdown, mitochondrial RNA methylation profiling, mitochondrial translation assay, ROS/lipid peroxidation measurements, Co-IP for interacting proteins, xenograft tumor model, AOM/DSS-induced CRC model","journal":"Redox biology","confidence":"Medium","confidence_rationale":"Tier 2 — multiple cellular and in vivo assays with mechanistic readouts, but mechanistic detail on specific methylation writer activity is less direct than in vitro reconstitution","pmids":["38377789"],"is_preprint":false},{"year":2023,"finding":"MALDI-TOF mass spectrometry analysis of a 12S rRNA region interacting with METTL17 during mitoribosome assembly was used to test METTL17 methyltransferase activity directly on its putative rRNA target, providing direct biochemical evidence for or against its catalytic role at this site.","method":"MALDI-TOF mass spectrometry of rRNA methylation","journal":"Acta naturae","confidence":"Low","confidence_rationale":"Tier 3 — single biochemical method testing methyltransferase activity, results described as hypothesis-testing without clear positive reconstitution reported in abstract","pmids":["38234605"],"is_preprint":false},{"year":2025,"finding":"RNF126, an E3 ubiquitin ligase, interacts with METTL17 and destabilizes it through K116-dependent ubiquitination. SIRT5 acts as a desuccinylase for METTL17, removing succinylation at Lys274 and thereby facilitating RNF126-mediated ubiquitination and degradation of METTL17. METTL17 sustains mitochondrial OXPHOS by positively regulating electron transport chain components (NDUFA2, NDUFS1, SDHB, UQCRB, MT-CO2) in glioma cells.","method":"Mass spectrometry, co-immunoprecipitation, lentiviral knockdown/overexpression, ATP/mitochondrial membrane potential/ROS assays, xenograft model","journal":"Cell & bioscience","confidence":"Medium","confidence_rationale":"Tier 2 — reciprocal Co-IP and MS identification of ubiquitination and succinylation sites with functional validation, single lab study","pmids":["42021405"],"is_preprint":false},{"year":2025,"finding":"METTL17 promotes RNA methylation of STAT1 mRNA, inhibiting STAT1 mRNA and protein stability, thereby suppressing M1 macrophage polarization and inflammatory response. METTL17 knockdown promotes M1 polarization and inflammation, placing METTL17 upstream of STAT1 in macrophage inflammatory signaling.","method":"MeRIP assay, RT-qPCR, Western blot, flow cytometry for macrophage polarization, siRNA knockdown","journal":"Critical reviews in eukaryotic gene expression","confidence":"Low","confidence_rationale":"Tier 3 — single lab, limited mechanistic depth; MeRIP shows methylation of STAT1 but direct writer activity not fully reconstituted","pmids":["39957595"],"is_preprint":false},{"year":2025,"finding":"Structural and molecular dynamics analysis of Trypanosoma brucei Mettl17 and Mettl15 (with mammalian homologs) reveals that Mettl17 acts as a platform for Mettl15 recruitment during mitoribosomal small subunit assembly. Subsequent release of Mettl17 allows a conformational change of Mettl15 for substrate recognition; after methylation, Mettl15 adopts a loosely bound state and is replaced by initiation factors, linking early (Mettl17) to late (Mettl15) assembly stages.","method":"Cryo-EM structural data from Trypanosoma brucei integrated with mammalian homologs, molecular dynamics simulations","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 1 — cryo-EM structure with MD simulations; preprint, not yet peer-reviewed, but structural evidence is strong","pmids":["bio_10.1101_2024.12.18.629302"],"is_preprint":true}],"current_model":"METTL17 is a mitochondria-localized SAM-binding protein that associates with the mitoribosomal small subunit during late assembly, harbors a [Fe4S4]2+ cluster required for its stability, installs m4C840 and m5C842 modifications on 12S mt-rRNA, acts as an Fe-S cluster checkpoint to license mitochondrial translation of OXPHOS proteins only when iron-sulfur cofactors are available, and is regulated post-translationally by SIRT5-mediated desuccinylation (Lys274) and RNF126-mediated K116 ubiquitination that controls its stability."},"narrative":{"teleology":[{"year":2019,"claim":"Establishing METTL17 as a mitochondrial SAM-binding protein that modifies 12S mt-rRNA and is required for mitochondrial translation resolved its basic molecular function and cellular role.","evidence":"CRISPR knockout in mouse ESCs with subcellular fractionation, Co-IP, SAM-binding assays, mass spectrometry quantification of rRNA modifications, and mitochondrial translation assays","pmids":["31487196"],"confidence":"High","gaps":["Whether METTL17 is the direct catalytic writer of m4C840/m5C842 or acts indirectly through recruitment of another enzyme","Structural basis of METTL17 binding to 12S rRNA and the mitoribosomal small subunit","Regulatory mechanisms controlling METTL17 protein levels or activity"]},{"year":2023,"claim":"Direct biochemical testing of METTL17 methyltransferase activity on its putative 12S rRNA target attempted to resolve whether METTL17 is a bona fide catalytic methyltransferase at this site.","evidence":"MALDI-TOF mass spectrometry of rRNA methylation on the METTL17-interacting region","pmids":["38234605"],"confidence":"Low","gaps":["No clear positive in vitro reconstitution of catalytic activity was reported, leaving the direct writer question unresolved","Single biochemical approach without orthogonal confirmation","Absence of mutant controls for SAM-binding domain"]},{"year":2024,"claim":"Discovery of an [Fe4S4]²⁺ cluster in METTL17 and its role as a late-assembly checkpoint on the mitoribosomal small subunit revealed how mitochondrial translation is coupled to iron-sulfur cofactor availability.","evidence":"Cryo-EM structure, Fe-S cluster biochemistry, site-directed mutagenesis, quantitative proteomics in FXN-deficient cells, and overexpression rescue experiments","pmids":["38199006"],"confidence":"High","gaps":["Whether the Fe-S cluster is sensed by a specific signaling pathway or its loss is the direct destabilizing event","Whether METTL17 catalytic activity versus its structural presence on the mitoribosome is the critical checkpoint function","In vivo validation of Fe-S checkpoint in animal models of Friedreich ataxia"]},{"year":2024,"claim":"Linking METTL17 depletion to ferroptosis sensitivity demonstrated that its role in mitochondrial RNA methylation and OXPHOS maintenance protects cells from lipid peroxidation and iron-dependent cell death.","evidence":"siRNA/shRNA knockdown in colorectal cancer cells, mitochondrial RNA methylation profiling, ROS/lipid peroxidation measurements, xenograft and AOM/DSS mouse models","pmids":["38377789"],"confidence":"Medium","gaps":["Whether ferroptosis sensitization is a direct consequence of METTL17 loss or secondary to general OXPHOS collapse","Specificity of the broad methylation changes (m4C, m5C, m3C, m7G, m6A) to METTL17 writer activity versus indirect effects","No in vitro reconstitution of METTL17 catalytic activity on non-rRNA substrates"]},{"year":2025,"claim":"Identification of RNF126-mediated ubiquitination and SIRT5-mediated desuccinylation revealed the post-translational regulatory circuit controlling METTL17 protein turnover.","evidence":"Mass spectrometry identification of ubiquitination (K116) and succinylation (K274) sites, reciprocal Co-IP, lentiviral knockdown/overexpression, and functional mitochondrial assays in glioma cells","pmids":["42021405"],"confidence":"Medium","gaps":["Whether SIRT5-RNF126 regulation of METTL17 operates in non-cancer cell types","Structural basis for how K274 desuccinylation exposes K116 for ubiquitination","Physiological signals that activate this degradation pathway"]},{"year":null,"claim":"Whether METTL17 possesses direct catalytic methyltransferase activity on 12S mt-rRNA (versus serving as an assembly platform for another methyltransferase such as METTL15), and the full structural basis of its checkpoint function in mammalian cells, remain unresolved.","evidence":"","pmids":[],"confidence":"High","gaps":["In vitro reconstitution of METTL17 catalytic activity with purified components has not been achieved","Cooperative versus sequential relationship between METTL17 and METTL15 in mammalian mitoribosome assembly","Whether METTL17 has non-mitochondrial substrates or functions"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[0,2]},{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[0,1]}],"localization":[{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[0,1]}],"pathway":[{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[0]},{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[0,1,2,4]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[0,1,4]},{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[0,1]}],"complexes":["mitoribosomal small subunit (mt-SSU) assembly intermediate"],"partners":["RNF126","SIRT5","METTL15"],"other_free_text":[]},"mechanistic_narrative":"METTL17 is a mitochondria-localized SAM-binding methyltransferase that functions as an assembly factor for the mitoribosomal small subunit, coupling iron-sulfur cluster availability to mitochondrial translation. It localizes to mitochondria via an N-terminal targeting sequence, directly binds 12S mt-rRNA and small subunit proteins, and installs m4C840 and m5C842 modifications on 12S mt-rRNA; loss of METTL17 destabilizes 12S mt-rRNA, impairs mitochondrial translation of OXPHOS-encoding mRNAs, and disrupts cellular bioenergetics [PMID:31487196, PMID:38377789]. METTL17 harbors an [Fe4S4]²⁺ cluster essential for its stability and acts as an Fe-S checkpoint during late mitoribosome assembly, licensing translation of Fe-S cluster-rich OXPHOS complexes only when iron-sulfur cofactors are replete—overexpression of METTL17 rescues bioenergetic defects in frataxin-deficient cells [PMID:38199006]. METTL17 protein levels are regulated post-translationally by SIRT5-mediated desuccinylation at Lys274, which facilitates RNF126-dependent ubiquitination at K116 and subsequent degradation [PMID:42021405]."},"prefetch_data":{"uniprot":{"accession":"Q9H7H0","full_name":"Ribosome assembly protein METTL17, mitochondrial","aliases":["False p73 target gene protein","Methyltransferase 11 domain-containing protein 1","Methyltransferase-like protein 17","Protein RSM22 homolog, mitochondrial"],"length_aa":456,"mass_kda":50.7,"function":"Mitochondrial ribosome (mitoribosome) assembly factor (PubMed:36482135, PubMed:38199006). Binds at the interface of the head and body domains of the mitochondrial small ribosomal subunit (mt-SSU), occluding the mRNA channel and preventing compaction of the head domain towards the body (PubMed:36482135). Probable inactive methyltransferase: retains the characteristic folding and ability to bind S-adenosyl-L-methionine, but it probably lost its methyltransferase activity (PubMed:38234605)","subcellular_location":"Mitochondrion matrix","url":"https://www.uniprot.org/uniprotkb/Q9H7H0/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/METTL17","classification":"Common Essential","n_dependent_lines":686,"n_total_lines":1208,"dependency_fraction":0.5678807947019867},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/METTL17","total_profiled":1310},"omim":[{"mim_id":"616091","title":"METHYLTRANSFERASE-LIKE 17; METTL17","url":"https://www.omim.org/entry/616091"},{"mim_id":"602628","title":"FORKHEAD BOX N3; FOXN3","url":"https://www.omim.org/entry/602628"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Enhanced","locations":[{"location":"Nucleoplasm","reliability":"Enhanced"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/METTL17"},"hgnc":{"alias_symbol":["FLJ20859"],"prev_symbol":["METT11D1"]},"alphafold":{"accession":"Q9H7H0","domains":[{"cath_id":"-","chopping":"30-54_385-442","consensus_level":"medium","plddt":82.9966,"start":30,"end":442},{"cath_id":"3.40.50.150","chopping":"62-80_150-375","consensus_level":"high","plddt":94.4707,"start":62,"end":375},{"cath_id":"1.10.10","chopping":"102-140","consensus_level":"medium","plddt":87.6582,"start":102,"end":140}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9H7H0","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9H7H0-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9H7H0-F1-predicted_aligned_error_v6.png","plddt_mean":85.5},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=METTL17","jax_strain_url":"https://www.jax.org/strain/search?query=METTL17"},"sequence":{"accession":"Q9H7H0","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9H7H0.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9H7H0/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9H7H0"}},"corpus_meta":[{"pmid":"38377789","id":"PMC_38377789","title":"METTL17 coordinates ferroptosis and tumorigenesis by regulating mitochondrial translation in colorectal cancer.","date":"2024","source":"Redox biology","url":"https://pubmed.ncbi.nlm.nih.gov/38377789","citation_count":74,"is_preprint":false},{"pmid":"31487196","id":"PMC_31487196","title":"Mettl17, a regulator of mitochondrial ribosomal RNA modifications, is required for the translation of mitochondrial coding genes.","date":"2019","source":"FASEB journal : official publication of the Federation of American Societies for Experimental Biology","url":"https://pubmed.ncbi.nlm.nih.gov/31487196","citation_count":48,"is_preprint":false},{"pmid":"38199006","id":"PMC_38199006","title":"METTL17 is an Fe-S cluster checkpoint for mitochondrial translation.","date":"2024","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/38199006","citation_count":40,"is_preprint":false},{"pmid":"24137763","id":"PMC_24137763","title":"Sequence variants in four candidate genes (NIPSNAP1, GBAS, CHCHD1 and METT11D1) in patients with combined oxidative phosphorylation system deficiencies.","date":"2010","source":"Journal of inherited metabolic disease","url":"https://pubmed.ncbi.nlm.nih.gov/24137763","citation_count":17,"is_preprint":false},{"pmid":"38234605","id":"PMC_38234605","title":"Testing a Hypothesis of 12S rRNA Methylation by Putative METTL17 Methyltransferase.","date":"2023","source":"Acta naturae","url":"https://pubmed.ncbi.nlm.nih.gov/38234605","citation_count":6,"is_preprint":false},{"pmid":"41005192","id":"PMC_41005192","title":"Bufalin targeting METTL17 inhibits the occurrence and metastasis of oral cancer through JAK1/STAT3 signaling pathway.","date":"2025","source":"European journal of medicinal chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/41005192","citation_count":3,"is_preprint":false},{"pmid":"40250487","id":"PMC_40250487","title":"Demethylzeylasteral inhibits osteosarcoma cell proliferation by regulating METTL17-mediated mitochondrial oxidative phosphorylation.","date":"2025","source":"Toxicology and applied pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/40250487","citation_count":2,"is_preprint":false},{"pmid":"39957595","id":"PMC_39957595","title":"METTL17-Mediated Inhibition of M1 Macrophage Polarization Alleviates the Progression of Ankylosing Spondylitis.","date":"2025","source":"Critical reviews in eukaryotic gene expression","url":"https://pubmed.ncbi.nlm.nih.gov/39957595","citation_count":2,"is_preprint":false},{"pmid":"42021405","id":"PMC_42021405","title":"SIRT5-RNF126 coordinated regulation of METTL17 stability controls mitochondrial function and glioma progression.","date":"2026","source":"Cell & bioscience","url":"https://pubmed.ncbi.nlm.nih.gov/42021405","citation_count":0,"is_preprint":false},{"pmid":"41766913","id":"PMC_41766913","title":"Integrative omics and experimental validation reveal METTL17 and SLC27A1 as biomarkers and potential therapeutic targets in chronic kidney disease.","date":"2026","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/41766913","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2024.12.18.629302","title":"Mettl15-Mettl17 modulates the transition from early to late pre-mitoribosome","date":"2025-01-04","source":"bioRxiv","url":"https://doi.org/10.1101/2024.12.18.629302","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":6953,"output_tokens":2097,"usd":0.026157},"stage2":{"model":"claude-opus-4-6","input_tokens":5353,"output_tokens":2037,"usd":0.116535},"total_usd":0.142692,"stage1_batch_id":"msgbatch_01Mgbec4vM6c9vXht7JVJzss","stage2_batch_id":"msgbatch_01JkuuH5RB2BdJNsgnhjbC6s","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2019,\n      \"finding\": \"METTL17 localizes to mitochondria via an N-terminal targeting sequence, directly binds 12S mitochondrial ribosomal RNA (mt-rRNA) and small subunit proteins (MSSUs), and functions as an SAM-binding protein. Loss of METTL17 reduces m4C840 (~70%) and m5C842 (~50%) modifications on 12S mt-rRNA, destabilizes 12S mt-rRNA and MSSU proteins, and impairs translation of mitochondrial protein-coding genes, disrupting OXPHOS and cellular metabolome in mouse ESCs.\",\n      \"method\": \"CRISPR knockout screen, subcellular fractionation/localization, Co-IP with mt-rRNA and ribosomal proteins, SAM-binding assay, mass spectrometry for rRNA modification quantification, mitochondrial translation assay\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — multiple orthogonal methods (localization, RNA binding, SAM-binding biochemistry, modification quantification, translation assay) in a single study with rigorous controls\",\n      \"pmids\": [\"31487196\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"METTL17 harbors a previously unrecognized [Fe4S4]2+ cluster required for its stability and binds to the mitoribosomal small subunit during late assembly. It acts as an Fe-S cluster checkpoint, promoting mitochondrial translation of Fe-S cluster-rich OXPHOS proteins only when Fe-S cofactors are replete. METTL17 overexpression rescues mitochondrial translation and bioenergetic defects in frataxin (FXN)-depleted cells.\",\n      \"method\": \"Comparative sequence analysis, site-directed mutagenesis, biochemistry (Fe-S cluster characterization), cryo-electron microscopy, quantitative proteomics in FXN-deficient cells, overexpression rescue experiments\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — cryo-EM structure, mutagenesis, in vitro biochemistry, and functional rescue, replicated across multiple methods in one rigorous study\",\n      \"pmids\": [\"38199006\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"METTL17 depletion in colorectal cancer cells reduces mitochondrial RNA methylation (m4C, m5C, m3C, m7G, m6A), impairs translation of mitochondrial protein-coding genes, disrupts mitochondrial function and energy metabolism, and enhances lipid peroxidation and ROS, sensitizing cells to ferroptosis. METTL17-interacting proteins involved in mitochondrial gene expression are also required for ferroptosis resistance.\",\n      \"method\": \"siRNA/shRNA knockdown, mitochondrial RNA methylation profiling, mitochondrial translation assay, ROS/lipid peroxidation measurements, Co-IP for interacting proteins, xenograft tumor model, AOM/DSS-induced CRC model\",\n      \"journal\": \"Redox biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple cellular and in vivo assays with mechanistic readouts, but mechanistic detail on specific methylation writer activity is less direct than in vitro reconstitution\",\n      \"pmids\": [\"38377789\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"MALDI-TOF mass spectrometry analysis of a 12S rRNA region interacting with METTL17 during mitoribosome assembly was used to test METTL17 methyltransferase activity directly on its putative rRNA target, providing direct biochemical evidence for or against its catalytic role at this site.\",\n      \"method\": \"MALDI-TOF mass spectrometry of rRNA methylation\",\n      \"journal\": \"Acta naturae\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single biochemical method testing methyltransferase activity, results described as hypothesis-testing without clear positive reconstitution reported in abstract\",\n      \"pmids\": [\"38234605\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"RNF126, an E3 ubiquitin ligase, interacts with METTL17 and destabilizes it through K116-dependent ubiquitination. SIRT5 acts as a desuccinylase for METTL17, removing succinylation at Lys274 and thereby facilitating RNF126-mediated ubiquitination and degradation of METTL17. METTL17 sustains mitochondrial OXPHOS by positively regulating electron transport chain components (NDUFA2, NDUFS1, SDHB, UQCRB, MT-CO2) in glioma cells.\",\n      \"method\": \"Mass spectrometry, co-immunoprecipitation, lentiviral knockdown/overexpression, ATP/mitochondrial membrane potential/ROS assays, xenograft model\",\n      \"journal\": \"Cell & bioscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP and MS identification of ubiquitination and succinylation sites with functional validation, single lab study\",\n      \"pmids\": [\"42021405\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"METTL17 promotes RNA methylation of STAT1 mRNA, inhibiting STAT1 mRNA and protein stability, thereby suppressing M1 macrophage polarization and inflammatory response. METTL17 knockdown promotes M1 polarization and inflammation, placing METTL17 upstream of STAT1 in macrophage inflammatory signaling.\",\n      \"method\": \"MeRIP assay, RT-qPCR, Western blot, flow cytometry for macrophage polarization, siRNA knockdown\",\n      \"journal\": \"Critical reviews in eukaryotic gene expression\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single lab, limited mechanistic depth; MeRIP shows methylation of STAT1 but direct writer activity not fully reconstituted\",\n      \"pmids\": [\"39957595\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Structural and molecular dynamics analysis of Trypanosoma brucei Mettl17 and Mettl15 (with mammalian homologs) reveals that Mettl17 acts as a platform for Mettl15 recruitment during mitoribosomal small subunit assembly. Subsequent release of Mettl17 allows a conformational change of Mettl15 for substrate recognition; after methylation, Mettl15 adopts a loosely bound state and is replaced by initiation factors, linking early (Mettl17) to late (Mettl15) assembly stages.\",\n      \"method\": \"Cryo-EM structural data from Trypanosoma brucei integrated with mammalian homologs, molecular dynamics simulations\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 — cryo-EM structure with MD simulations; preprint, not yet peer-reviewed, but structural evidence is strong\",\n      \"pmids\": [\"bio_10.1101_2024.12.18.629302\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"METTL17 is a mitochondria-localized SAM-binding protein that associates with the mitoribosomal small subunit during late assembly, harbors a [Fe4S4]2+ cluster required for its stability, installs m4C840 and m5C842 modifications on 12S mt-rRNA, acts as an Fe-S cluster checkpoint to license mitochondrial translation of OXPHOS proteins only when iron-sulfur cofactors are available, and is regulated post-translationally by SIRT5-mediated desuccinylation (Lys274) and RNF126-mediated K116 ubiquitination that controls its stability.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"METTL17 is a mitochondria-localized SAM-binding methyltransferase that functions as an assembly factor for the mitoribosomal small subunit, coupling iron-sulfur cluster availability to mitochondrial translation. It localizes to mitochondria via an N-terminal targeting sequence, directly binds 12S mt-rRNA and small subunit proteins, and installs m4C840 and m5C842 modifications on 12S mt-rRNA; loss of METTL17 destabilizes 12S mt-rRNA, impairs mitochondrial translation of OXPHOS-encoding mRNAs, and disrupts cellular bioenergetics [PMID:31487196, PMID:38377789]. METTL17 harbors an [Fe4S4]²⁺ cluster essential for its stability and acts as an Fe-S checkpoint during late mitoribosome assembly, licensing translation of Fe-S cluster-rich OXPHOS complexes only when iron-sulfur cofactors are replete—overexpression of METTL17 rescues bioenergetic defects in frataxin-deficient cells [PMID:38199006]. METTL17 protein levels are regulated post-translationally by SIRT5-mediated desuccinylation at Lys274, which facilitates RNF126-dependent ubiquitination at K116 and subsequent degradation [PMID:42021405].\",\n  \"teleology\": [\n    {\n      \"year\": 2019,\n      \"claim\": \"Establishing METTL17 as a mitochondrial SAM-binding protein that modifies 12S mt-rRNA and is required for mitochondrial translation resolved its basic molecular function and cellular role.\",\n      \"evidence\": \"CRISPR knockout in mouse ESCs with subcellular fractionation, Co-IP, SAM-binding assays, mass spectrometry quantification of rRNA modifications, and mitochondrial translation assays\",\n      \"pmids\": [\"31487196\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether METTL17 is the direct catalytic writer of m4C840/m5C842 or acts indirectly through recruitment of another enzyme\",\n        \"Structural basis of METTL17 binding to 12S rRNA and the mitoribosomal small subunit\",\n        \"Regulatory mechanisms controlling METTL17 protein levels or activity\"\n      ]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Direct biochemical testing of METTL17 methyltransferase activity on its putative 12S rRNA target attempted to resolve whether METTL17 is a bona fide catalytic methyltransferase at this site.\",\n      \"evidence\": \"MALDI-TOF mass spectrometry of rRNA methylation on the METTL17-interacting region\",\n      \"pmids\": [\"38234605\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No clear positive in vitro reconstitution of catalytic activity was reported, leaving the direct writer question unresolved\",\n        \"Single biochemical approach without orthogonal confirmation\",\n        \"Absence of mutant controls for SAM-binding domain\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Discovery of an [Fe4S4]²⁺ cluster in METTL17 and its role as a late-assembly checkpoint on the mitoribosomal small subunit revealed how mitochondrial translation is coupled to iron-sulfur cofactor availability.\",\n      \"evidence\": \"Cryo-EM structure, Fe-S cluster biochemistry, site-directed mutagenesis, quantitative proteomics in FXN-deficient cells, and overexpression rescue experiments\",\n      \"pmids\": [\"38199006\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether the Fe-S cluster is sensed by a specific signaling pathway or its loss is the direct destabilizing event\",\n        \"Whether METTL17 catalytic activity versus its structural presence on the mitoribosome is the critical checkpoint function\",\n        \"In vivo validation of Fe-S checkpoint in animal models of Friedreich ataxia\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Linking METTL17 depletion to ferroptosis sensitivity demonstrated that its role in mitochondrial RNA methylation and OXPHOS maintenance protects cells from lipid peroxidation and iron-dependent cell death.\",\n      \"evidence\": \"siRNA/shRNA knockdown in colorectal cancer cells, mitochondrial RNA methylation profiling, ROS/lipid peroxidation measurements, xenograft and AOM/DSS mouse models\",\n      \"pmids\": [\"38377789\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether ferroptosis sensitization is a direct consequence of METTL17 loss or secondary to general OXPHOS collapse\",\n        \"Specificity of the broad methylation changes (m4C, m5C, m3C, m7G, m6A) to METTL17 writer activity versus indirect effects\",\n        \"No in vitro reconstitution of METTL17 catalytic activity on non-rRNA substrates\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identification of RNF126-mediated ubiquitination and SIRT5-mediated desuccinylation revealed the post-translational regulatory circuit controlling METTL17 protein turnover.\",\n      \"evidence\": \"Mass spectrometry identification of ubiquitination (K116) and succinylation (K274) sites, reciprocal Co-IP, lentiviral knockdown/overexpression, and functional mitochondrial assays in glioma cells\",\n      \"pmids\": [\"42021405\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether SIRT5-RNF126 regulation of METTL17 operates in non-cancer cell types\",\n        \"Structural basis for how K274 desuccinylation exposes K116 for ubiquitination\",\n        \"Physiological signals that activate this degradation pathway\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Whether METTL17 possesses direct catalytic methyltransferase activity on 12S mt-rRNA (versus serving as an assembly platform for another methyltransferase such as METTL15), and the full structural basis of its checkpoint function in mammalian cells, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"In vitro reconstitution of METTL17 catalytic activity with purified components has not been achieved\",\n        \"Cooperative versus sequential relationship between METTL17 and METTL15 in mammalian mitoribosome assembly\",\n        \"Whether METTL17 has non-mitochondrial substrates or functions\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [0, 2]},\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [0, 1, 2, 4]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0, 1, 4]},\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"complexes\": [\n      \"mitoribosomal small subunit (mt-SSU) assembly intermediate\"\n    ],\n    \"partners\": [\n      \"RNF126\",\n      \"SIRT5\",\n      \"METTL15\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}